Varactor folding technique for phase noise reduction in electronic oscillators

Abstract

A varactor folding technique reduces noise in controllable electronic oscillators through the use of a series of varactors having relatively small capacitance. A folding circuit provides control signals to the varactors in a sequential manner to provide a relatively smooth change in the total capacitance of the oscillator. Consequently, effective control of the oscillator is achieved with accompanying reductions in oscillator noise such as flicker noise.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a continuation of U.S. patent application Ser. No. 10,395,116, filed Mar. 25, 2003 now U.S. Pat. No. 6,806,787, which is a divisional of U.S. patent application Ser. No. 09,738,858, filed Dec. 14, 2000 now U.S. Pat. No. 6,563,392, which claims the benefit of the U.S. Provisional Application No. 60,170,840, filed Dec. 14, 1999, all of which are incorporated herein by reference in their entireties.BACKGROUND OF THE INVENTION[0002]Communication systems use oscillators to process various signals used in the communication process. In a typical communication system, an information signal (e.g., a television program) is modulated onto a high frequency carrier signal to facilitate transmission of the signal. Such modulation may be accomplished, for example, by varying the phase of the carrier signal according to the information in the signal. Through the use of different carrier signals of different frequencies, many informatio...

AI Technical Summary

Benefits of technology

This approach significantly reduces phase noise in oscillators, allowing for improved signal quality and reduced noise interference, enabling more effective phase modulation and channel rejection.

Problems solved by technology

Fluctuations in the phase of the transmitter or receiver oscillators corrupt the intended phase modulation of the signal in systems which use phase or frequency modulation.

Phase noise may also reduce the ability of a radio system to reject or discern unwanted channels close in frequency to the desired channel.

Nevertheless, system performance is often limited by the quality of available oscillators at practical levels of cost, size, and power dissipation.

Oscillators also may suffer from a significant level of noise due to up-conversion of flicker (1 / f) noise from low frequencies to near the center frequency of the oscillator.

Flicker noise occurs at low frequencies in nearly all electronic components.

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